Welting of styrene-butadiene copolymer



July 3, 1951 A. R. OLSON ETAL 2,558,776

WELTING OF STYRENE-BUTADIENE COPOLYMER Filed July 23, 1947 Patented July 3, 1 951 UNITED s'rAr WELTING OF. STYRENE-BUTAD'IENE COPOLYMER Arthur R. Olson, Cambridge, and Edward B.

McMillan, Salem, Mass., assignors to United Shoe Machinery Corporation, Flemingtom N. J a corporation of New Jersey Applicationv July 23, 1947, Serial No. 763,052

' manufacturer in rolls and with each strip having a length of several yards. Such rolls have proven to be a convenient form for handling the welting prior'to and as it is attached to the uppers and the insoles of shoes. The dimensions of such long strips of leather welting are not always uniform and the joints sometimes give trouble not only during the making of the shoes but also while the shoes are in service.

Continuous strips of plastic welting have been produced hitherto and the necessity for joints has thereby been eliminated but such welting has had inherent disadvantages. It has been found that plastic welting as known prior to the present invention tended to become too rigid with age and/or upon being subjected to low temperatures. Chemical plasticizers are essential in such welting, and aging results in a loss of the plasticizer and this loss changes the characteristics of the welting. Treatment of conventional plastic welting in an electronic field for sole attaching purposes (as an example) causes the welting to distort slightly, destroying the trim appearance of the shoe. High frequency heating also causes such welting to soften unduly. Pr'oper placement or arrangement of such welting relative to the shoe upper and sole is diificult and this has proven to be so particularly in the toe and inside shank areas. Many disadvantages are found in the use of conventional plastic welting as will further appear and for this reason acceptance of such welting has encountered resistance.

According to the present invention there is provided a novel welt to which an outsole may be stitched or cemented, the welt comprising styrene-butadiene copolymer with a high styrene content.

Referring to the accompanying drawings,

2 Claims. (CI. 36-78) welting. A welt beating operation may be performed upon it or the welt may be pressed flat against the outsole and attached thereto during the sole laying operation. 'Stitch indenting may be carried out without slowing down the operation as heretofore commercially practiced in the use of leather welting, and heat need not be applied to the tool or knife used. The advantages are given in more comprehensive detail hereinafter.

Fig. 2 of the drawings shows a shoe upper 3, an insole at 5, an outsole at l, and the novel welting at 9. This form of shoe construction, with reference to the arrangement of the shoe parts, is to be recognized as conventional, the novelty existing only in the welting whether it be considered by itself or as incorporated in a shoe.

The novel welting is composed of styrene-butadiene copolymer resin, preferably substantially free of a liquid plasticizer, the ultimate composition being suitably modified by inert fillers and, in' some instances, a small amount of rubber to vary the hardness as well as elongation under stress. The copolymer is a material similar to Buna S but with a high styrene content. The characteristics of the compounded material are peculiarly adapted to meet the many and varied conditions to which welting is subjected. The material in welting must not be too rubbery and it must be such as to lend itself to rapid production in strip form by calendaring or extrusion. It must have proper hardness for the specific conditions which are be encountered by welting. It must have great Fig. 1 shows a roll of the novel welting with a stitch receiving groove and a bevel; and

Fig. 2 shows a portion of a shoe in which the stitch retaining capacity or strength for adhesion to a shoe upper or sole and it must easily conform to the last or toe of a shoe. It should have a capacity for stitch indentation, maintain desired flexibility despite a wide divergence of temperature, resist moisture penetration, yield itself to the addition of a suitable coloring agent, and be stable in so far as aging is concerned. The ingredients used in a given compounding may be varied within rather wide limits with a corresponding loss or gain in some of the welting characteristics.

Example 1 The following ingredients are put through a mill (cold or heated) Grams -30 type styrene-butadiene copolymer assure 3 The thermoplastic composition secured from the mill is then heated and extruded to form welting with a desired cross section and a stitch I receiving groove.

The 70-30 type styrene-butadiene copolymer (70 parts of styrene with 30 parts of butadiene) is such as is produced by Dewey I: Almy Chemical Co. of Cambridge, Massachusetts, and under the name of Dare: #3 and is the basic ingredient of the composition. The copolymer of the same general type'produced by the Goodyear- Tire 8: Rubber Co., Akron, Ohio, and designated as P-1799, may be used as the basic ingredient if desired. It will be noted that in the present example the percentage of copolymer in the composition by weight is 48.2

The 30-70 type styrene-butadiene copolymer (30 parts of styrene with 70 parts of butadiene) is a chief all-purpose rubber generally called GR-S and is used in the present example to reduce the stiffness of the product. It may be said to be a non-liquid plasticizer.

The calcium carbonate (Calcene-produced by Columbia Chemical Div. of Pittsburgh Plate Glass Co.) reduces the stretch of elongation under stress placed upon the welting in use but it does not contribute to the hardness.

The hydrated calcium silicate reduces the elongation and serves an additional purpose in that it increases the hardness. Without calcium carbonate in the present example, the calcium silicate would make the welting too hard. Phenyl-beta-naphthylamine is an antioxidant which is preferably added to stabilize the compound. The zinc stearate is added to aid in the extrusion operation.

Example 2 Grams 85-15 type styrene-butadiene copolymer" 150' 30-70 type styrene-butadiene copolymer 62 Phenyl-beta-naphthylamine 2.1 Dixie clay 100 The above ingredients are put through a mill with the 30-70 type copolymer and the clay being added in small quantities and alternatively.

The compound is then formed into welting by the use of hot rolls.

The 85-15 type of styrene-butadiene copolymer (85 parts of styrene with 15 parts of butadiene) is such as is produced by Dewey I: Almy Chemical Co. under the name of Darex #X34. The percentage of copolymer in the composition is 47.8%.

The GR-S or 30-70 type of copolymer is added as a larger proportion (comparing with Example 1) in order to avoid the stillness or rigidity imparted to the welting by the 85-15 type of copolymer.

Example 3 The following ingredients are put through a mill (cold or heated) The high styrene content copolymer is again the basic ingredient (488% of the composition) but it is to be noted that this particular com- 4 pounding is such that rubber or GR-S need not be added. v

The calcium carbonate (Kalvanproduced 7 the R. T. Vanderbilt Co. of New York, N. Y.) is

such as to possess ultra-fine particle size.

In order to produce a brown welting the coloring material used has the following composition:

Grams Rubber Orange FD 1.5 Rubber Red 213D .7 Rubber Monastral Fast Blue PCD 0.5

' These dyes are produced by the E. I. du Pont de Nemours 8: Co. of Wilmington, Delaware, but it is clear that pigments may be substituted therefor.

The welting of this particular example shows a very high resistance against stitch tear.

Example 4 Grams 70-30 type styrene-butadiene copolymer" 100 siliceous filler (Celite #270) 20 Calcium silicate (hydrated) 40 Phenyl-beta-naphthylamine 1.5 Zinc stearate 1.0 Coloring material (as in Example 3) 2.7

A composition with the above ingredients (the is taken from a milland extruded at a temperature of from 180 to 200 F. at the die head.

Celite #270 is produced by Johns-Manville Co. of New York, N. Y. It is a diatomaceous earth product marketed in the form of a light powder. The product is of a material which exhibits less resilience than do the welting compositions of Examples 1, 2 or 3-it closely resembles leather in this respect.

Experience hasshown that the welting composition, if it is to possess the advantages desired, should include the high styrene-butadiene copolymer as a base material (47.8 to 60.5% of the composition by weight) and that the styrene content in the copolymer should be from to 85 parts per hundred parts by weight. The -30 type copolymer is preferred for the base material as it leads to a most excellent product. It is to be understood that, if a copolymer of a different molecular weight (but within the range of 60 to partsof styrene per hundred parts of copolymer) is used, corresponding variations should be made in the compounding of the welt material in so far as the other ingredients are concerned in order to obtain the proper resiliency, toughness, etc. for welting.

Natural rubber and/or other elastomers which are compatible with the high styrene-butadiene copolymer may be used in place of the GR-S and with a corresponding change in the compounding.

It is to be appreciated that other fillers may be used in place of the calcium carbonate and calcium silicate although the formulation given in Example 1, above, has proved to be particularly excellent. It is clear that the filler should have low moisture absorption properties.

Vinyl compounds'such as copolymers of vinyl chloride and vinyl acetate, polyvinyl butyral, polyvinyl acetate and also plasticized polyvinyl chloride resins (such 'as referred to in United States Letters Patent No. 2,329,290, granted on an application filed in the name of Gay an: OGorman) are resins which possess o ly a few of the specific characteristics desired welting.

is The l compounds have been and are used to produce strong and attractive welting but such welting materials present difllculties for the following reasons:

(a) They are adversely affected by electronic heating;

(b) They cannot be loaded or extended (to any considerable extent) with inorganic fillers;

(0) They are not flexible until adequately plasticized;

(d) They gradually harden through loss of plasticizer;

(0) They stifien at low temperatures to which welting may well be subjected;

(f) Stitch indenting is diflicult;

(g) Vinyl compounds elongate considerably under heat and load;

(h) Welt beating operation cannot be satisfactorily performed; and

(i) The welting does not lend itself easily to edge trimming, setting and inseam trimming operations as the vinyl compounds "dive under the knife and to a much greater extent than does leather.

The nonvinyl compound or high-styrene butadiene copolymer welting of the present invention has been found to possess the following advantageous characteristics:

(a) The welting may be subjected to the action of an electronic field without distortion;

(b) The welting material may be loaded with inorganic flllers without detracting materially from its physical properties;

(0) It is flexible and does not need a plasticizer although one may be used in which event it does not migrate as rapidly as is the case with vinyl resins;

(d) It does not deteriorate with age, as preventative agents such as antioxidants may be used; t (e) Its flexibility is retained at low temperaure;

(1) The welting may be readily stitch indented;

(a) Elongation under heat and load is much less than in the case of vinyl welting;

(h) The welting is easily conformed and may be properly placed on a shoe to facilitate such operations as inseam stitching or sole attachin (i) The nonvinyl material will not dive excessively under the knife during edge trimming, setting and inseam trimming operations, 1. e., its reaction in this respect is similar to that of leather. 1

One of the most important characteristics of the novel welting is probably that listed under (h) above. The welting readily conforms itself to the edge curvature of the shoe during the inseam sewing operation and it does so without any tendency to snap back or spring back against the side of the shoe or against the tip at the toe end of the shoe even though the welting is not precurved or given a, different cross section to allow for bending about the toe. Straight strips of welting with conventional cross sections may be used and the result is a well fitted shoe with the welt accurately placed with relation to the upper and the sole.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. An article of manufacture comprising a welt having a stitch receiving groove therein, said welt being formed of nonplasticized plastic composition, said composition including a major portion of styrene-butadiene copolymer with a styrene content of from 60 to 65 parts per 100 parts of the copolymer by weight, and fillers giving proper characteristics for welting, said fillers being calcium carbonate and calcium silicate.

2. A shoe welt in the form of a strip of plastic composition having a stitch receiving groove therein, said strip having a suitable cross section for a shoe welt and being easily conformed for proper placement on a shoe, said composition comprising 47.8 to 60.5% by weight of styrene butadiene copolymer with a styrene content of from to parts per parts of the copolymer by weight, and a dry, finely divided filler of the group consisting of siliceous and carbonaceous materials which are inert in the composition and have low absorptive properties.

ARTHUR R. OLSON. EDWARD B. MCMIILAN.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS OTHER REFERENCES Industrial and Engineering Chemistry, vol. 38,

- N0. 9 (copy in Div. 50) pp. 955-958.

Modern Plastics Encyclopedia, 1948, p. 178. (Copy in Div. 11.)

Rubber Age (copy in Div. 50), May 1946, p. 211. 

1. AN ARTICLE OF MANUFACTURE COMPRISING A WELT HAVING A STITCH RECEIVING GROOVE THEREIN, SAID WELT BEING FORMED OF NONPLASTICIZED PLASTIC COMPOSITION, SAID COMPOSITION INCLUDING A MAJOR PORTION OF STYRENE-BUTADIENE COPOLYMER WITH A STYRENE CONTENT OF FROM 60 TO 65 PARTS PER 100 PARTS OF THE COPOLYMER BY WEIGHT, AND FILLERS GIVING PROPER CHARACTERISTICS FOR WELTING, SAID FILLERS BEING CALCIUM CARBONATE AND CALCIUM SILICATE. 